1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and, more particularly, to an image forming apparatus having a sorter for sorting and discharging a plurality of sheets respectively formed with identical images into a plurality of sort bins.
2. Description of Related Arts
Conventionally, copying machines have been widely used which electrophotographically make copies of a document original. Such copying machines are adapted to optically scan a document original, form an electrostatic latent image on a photoreceptor based on the scanned image, develop the electrostatic latent image into a toner image, and transfer the toner image onto a copy sheet.
These copying machines, if necessary, are provided with a sorter for sorting a plurality of copy sheets respectively formed with identical images. The sorter is adapted to discharge copy sheets each carrying an image of a document original transferred thereon into a single non-sort bin and to sort and discharge a plurality of copy sheets respectively formed with identical images into a plurality of sort bins when a plurality of copies are made from a single document original.
The copying machine with a sorter have a non-sort mode and a sort mode which are selectively set in the copying machine body thereof. In the non-sort mode, copy sheets formed with images are discharged into a non-sort bin. In the sort mode, copy sheets formed with images are discharged into sort bins.
Some of the copying machines with sorters can perform so-called post-processes when the sort mode is designated. The post-processes include a stapling process, a punching process and a stacking process. In the stapling process, a plurality of copy sheets discharged into each sort bin are stapled by means of a stapler. In the punching process, a plurality of copy sheets discharged into each sort bin are punched. In the stacking process, sets of copies which have been subjected to the stapling process are stacked in a stack section, so that the sets of copies can be easily taken out.
Where an error occurs during the stapling process in a copying machine with a sorter capable of performing such post-processes, for example, the entrance of a sort bin may be blocked by discharged copy sheets. The copy sheet blocking the entrance of the sort bin may interfere with the discharge of the next copy sheet formed with an image of a document original, thereby causing a jam. To avoid the jam, the copying machine is prohibited from performing a copying operation in the copying machine body thereof during the post-process.
Therefore, it takes time for the copying machine to return to a stand-by state for the next copying operation after the post-process. For example, about two to three seconds are required for stapling a set of copies. Therefore, the stapling of 20 sets of copies requires 40 seconds to one minute.
The copying machine further includes an image formation section for performing the copying operation to form an image on a copy sheet and, as required, optional-function performing means. The optional-function performing means include, for example, an automatic document original sheet feeder for feeding document original sheets one by one, a large volume sheet deck accommodating a large amount of copy sheets and having a lift for lifting the copy sheets to a position for feeding a copy sheet, an intermediate tray to be used for a two-side copying operation for forming images on both sides of a copy sheet, and the like.
These optional-function performing means are respectively controlled by independent controllers each comprising a microcomputer. The controllers are electrically connected to a central controller for controlling the entire operation of the copying machine as well as the operation of the image formation section.
When an error occurs in any of the optional-function performing means in the copying machine, the central controller is informed of the occurrence of the error. For example, a malfunction of a driving motor for driving a sheet feeding roller for taking in a document original sheet may occur in the automatic document original sheet feeder. At this time, a controller for controlling the automatic document original sheet feeder outputs an error occurrence signal to the central controller. In response thereto, the central controller prohibits the entire operation of the copying machine including a basic copying operation.
The sorter is also one of the optional-function performing means. Therefore, the operation of the sorter is controlled by an independent controller which is electrically connected to the central controller. When an error occurs in the sorter, the entire operation of the copying machine is prohibited. This is because the malfunction of the sorter may cause a jam and the like when a copy sheet formed with an image is discharged through the sorter.
Thus, the malfunction of the sorter prevents the copying machine from performing the copying operation. This means that a user cannot use the copying machine until a technical service person completes the repair of the sorter. That is, an office work requiring copy making is retarded. This problem is even more critical in case that the copying machine is used in a rural area where the user may have to wait for several days for the technical service person to come to repair the copying machine.